LAUSR

Abstract Structural properties of Pb-exchanged zeolites are of interest because of their applications in environmental remediation and in industrial processes. In this study, we report on a Pb-exchanged stellerite (Pb-STI), with particular focus on the cationic species, which form inside the zeolitic pores as a result of the exchange experiments. The produced zeolite had chemical composition Pb13.4(OH)10Al17.4Si54.6O144 ∙38H2O, indicating that Pb was uptaken in form of [Pb(OH)x](2-x) species. The STI framework maintained the Fmmm space group characteristic of the type material. However, the extraframework occupants, Pb2+, H2O and OH−, were characterized by a strong positional-disorder. The latter was resolved and interpreted combining Extended X-ray Absorption Fine Structure (EXAFS) analysis with Molecular Dynamics (MD) simulations. On average, Pb2+ ions are coordinated by 2 OH− and 1H2O at distances 2.8 A). Pb2+ adopts mainly a sided distorted coordination, indicating a stereochemical activity of the lone pair electrons. The obtained results were compared with those of other mono-cationic forms of STI zeolites. Based on the analysis of the framework distortion experienced after the incorporation of different metal ions, considerations are drawn on the potential effect of Pb2+ on the thermal stability of STI framework type zeolites.